Brilliant single-use web utility x.minutes.at puts a timed limit on any browser tab with ease. Got five minutes to browse Lifehacker but don't want to let that five minutes turn into 20? Visit http://5.minutes.at/lifehacker.com. Rinse and repeat for any site.

You can set a timer on any site or adjust the time limit by simply tweaking the URL. The Lifehacker URL above gives you five minutes to browse Lifehacker, but you could just as easily change it to 10.minutes.at/facebook.com, 15.minutes.at/flights+to+honolulu (which starts a Google search), or use a bookmarklet like 5.minutes.at/here to start a timer on a site you're already visiting. It loads the site in an iFrame, which means you can click around as much as you want and the timer will persist. When your time runs out, you'll see a Time's up! alert. Simple, smart, and cool, just how we like 'em.